Aflatoxins: New briefs disclose the threat to people and livestock and what research is doing about it

A damaged maize cob that, if harvested with clean cobs, can contaminate all the cobs with aflatoxins (photo credit: Joseph Atehnkeng/IITA).

‘The UN World Health Organization (WHO) estimates that billions of people in the developing world are chronically exposed to aflatoxin, a natural poison on food crops which causes cancer, impairs the immune system, inhibits growth, and causes liver disease as well as death in both humans and animals.

According to the International Food Policy Research Institute (IFPRI) aflatoxins contaminate one-quarter of the global food supply and over half the world’s population; 4.5 billion people are exposed to high, unmonitored levels, primarily in developing countries. In sub-Saharan African alone, an estimated 26,000 people die annually of liver cancer associated with aflatoxin exposure.

‘Aflatoxins not only pose serious health risks, but are believed to be detrimental to efforts to improve food security and international food trade.

‘According to the UN Food and Agricultural Organization (FAO), an estimated 25 percent of the world’s food crops are affected by aflatoxins.

‘This briefing looks at some of the efforts to combat aflatoxins, as well as the remaining challenges.

Children harvest groundnuts in West Africa (photo credit: IITA).

‘Aflatoxins are a naturally occurring carcinogenic by-product of common fungi on grains and other crops, particularly maize and groundnuts. They are a kind of mycotoxin, a highly toxic product of moulds that occurs on almost all agricultural commodities worldwide.

‘Aflatoxins are one of the most potent naturally occurring toxic substances; they are produced by fungi known as Aspergillus flavus.

‘Aflatoxin is not always obvious, and even grains that appear normal could actually be infested with high levels of the toxin-producing fungus, which thrives under poor storage conditions.

While the presence of moulds might be an indicator of the toxin, “it is a highly imperfect indicator of aflatoxin contamination,” according to the Consultative Group on International Agricultural Research. . . .

‘According to IFPRI, “Maize and peanuts are the main sources of human exposure to aflatoxin because they are so highly consumed worldwide.” Unfortunately, they are “the most susceptible crops to aflatoxin contamination.”. . .

‘Animal products such as milk and cheese, as well as cottonseed, spices and some feeds, are also prone to contamination from aflatoxins.

According to Johanna Lindahl, an epidemiologist at the International Livestock Research Institute (ILRI), “Very few know about the harm aflatoxins have on animals or even that animal food products can be contaminated with it as well.”

For instance, a study carried out in Nairobi by ILRI revealed that only 50 percent of those who had heard about aflatoxins believed it could be present in milk.

ILRI’s Lindahl, however, told IRIN that “milk and other dairy products can add to the total exposure of aflatoxin in humans,” and that it is necessary to accurately assess the risks.

Increased urbanization, coupled with an upsurge in urban livestock rearing, could increase the vulnerability of animals and animal products to aflatoxin contamination, said Lindahl.

‘When food crops are colonized by the fungi that produce aflatoxins in the field or during storage, they are rendered unsafe both for human and livestock consumption. . . .

Acute exposure to high levels of aflatoxins leads to aflatoxicosis, which can result in rapid death from liver failure.

‘Aflatoxin contamination has also been associated with childhood stunting.

Erastus Kangethe, food safety expert at the University of Nairobi, told IRIN, “It would be detrimental to ignore the long-term effects of aflatoxin, because unless we can control it, then we are going to witness a generation of stunted population very soon.”. . .

‘There are bio-control studies taking place in various African countries to help combat aflatoxin contamination in crops and animal products. Biological methods such as aflasafe — a biological control agent against aflatoxins — have shown to be effective.

In Nigeria, where field testing of aflasafe has already been done, Charity Mutegi, a scientist at the International Institute for Tropical Agriculture (IITA), told IRIN, “The efficacy results have been very positive. Aflatoxin contamination was reduced by between 80 to 90 percent both in maize and in groundnuts.”

According to the International Maize and Wheat Improvement Centre (CIMMYT), “Aflasafe works by ‘pushing out’ harmful, toxin-producing strains of A. flavus (the aflatoxin-causing fungi) from the field, through the deliberate introduction of indigenous but non-toxic, harmless strains — a process known as ‘competitive exclusion’.”

‘The lack of knowledge about aflatoxin detection among smallholders and the absence of widely available detection tools remain some of the biggest challenges in the control of aflatoxins. . . .

‘Experts have recommended more investments in scientific research to develop aflatoxin-resistant crop varieties, and say there is a need to create awareness among farmers about its dangers and how to detect the fungal poison. . . .

Read 19 briefs on aflatoxins published on 5 Nov 2013. The briefs were co-edited by Laurian Unnevehr, senior research fellow at IFPRI and theme leader for value chains for enhanced nutrition in the CGIAR Research Program on Agriculture for Nutrition and Health (A4NH), and Delia Grace, veterinary epidemiologist and food safety expert at the International Livestock Research Institute (ILRI) and theme leader for agriculture-associated diseases in A4NH.

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Increased urbanization, coupled with an upsurge in urban livestock rearing, could increase the vulnerability of animals and animal products to aflatoxin contamination, said Lindahl.